Traditionally, soap bars are composed of mixtures of soluble fatty acid soaps (which deliver lather benefits) and insoluble fatty acid soaps (which confer bar structure). For a variety of reasons, it may be desirable to reduce the levels of soluble and insoluble surfactant components in bar compositions, whether their components be soluble and insoluble fatty acid soaps or soluble and insoluble synthetic surfactant. High levels of surfactant, particularly if the surfactant is fatty acid soap for example, may decrease mildness.
A reduction in surfactant level, however, may have other consequences. For example, reduction in insoluble surfactant (e.g., insoluble fatty acids) must be accompanied by an increase in the level of fillers or other ingredients which in turn may lead to higher rates of wear. Also, for example, it would be expected that a reduced level of soluble surfactant would decrease foam generation, whereas foam is a desirable consumer cue of good cleansing.
As noted, it might be expected that reducing the level of surfactant (e.g., to increase mildness) and replacing the surfactant instead with fillers would lead to high rates of bar wear and poor foam properties (see, for example, U.S. Pat. No. 6,462,002 to Saxena et al.).
Unexpectedly, however, applicants have found that it is possible to avoid or minimize the use of insoluble fatty acids (which enhance structure but inhibit foam) by using bars which have initially high levels (e.g., greater than about 40%) of sugar. The high levels of sugar have been found to confer structure even with little or no insoluble fatty acid, while avoiding the foam depressing effects of insoluble fatty acids. Further, because of the low surfactant levels, the bars provide enhanced mildness. Further, the sugars (e.g., sucrose and disaccharides) are inexpensive and can easily be incorporated into soap bars.
Bars disclosed in the art typically may have relatively high levels of surfactants and relatively low levels of hydrophilic emollients. WO 02/50226 (Unilever), for example, discloses a low water cleansing bar comprising 15% to 60% by wt. surfactant and hydrophilic emollient (which may include polyhydric alcohols such as glycerine and propylene glycol, and polyols such as polyethylene glycols) at levels of 5 to 20%.
Similarly, U.S. Pat. No. 6,376,441 B1 to Ross et al. discloses multi-phase melt cast bars wherein, according to the examples, soap is present at about 40% by wt. and the level of sugar is about 16.8% (delivered as a 70% sucrose solution in water).
Other documents of interest may include the following: U.S. Pat. No. 6,458,751 to Abbas et al.; U.S. Pat. No. 6,384,000 to McFann et al.; U.S. Pat. No. 6,383,999 to Coyle et al.; U.S. Pat. No. 6,224,812 to Allan et al.; U.S. Pat. No. 6,174,845 to Rattinger et al.; WO 2002/061030 to Abbas et al., and WO 01/58422 to Coyle et al.
In none of the art is there believed disclosed bars having relatively low levels (e.g. less than about 25% by wt.) of surfactants comprising soluble fatty acid soaps and detergents and little (less than 5%, preferably less than 3%, more preferably less than 2% and most preferably less than 1%) or no insoluble fatty acid soaps; all in combination with high levels (greater than about 40%, preferably greater than about 50%) of sugars. Further, there is no disclosure that bars of such composition were they hypothetically even made, could avoid browning only if processed in a particular way.
In this regard, a second embodiment of the invention relates to a process for making sugar bars noted above and, in particular to a process for making whiter bars by ensuring that a glass transition modifier which is used in the composition is added after the neutralization of fatty acid.